Braking mechanism



Nov. 16, 1965 R. GARY BRAKING MECHANISM 2 Sheets-Sheet 1 Filed Jan. 10, 1963 INVENTOR.

Nov. 16, 1965 R. GARY 3,217,367

BRAKING MECHANISM Filed Jan. 10, 1963 2 Sheets-Sheet 2 3,217,367 BRAKING MECHANISM Robert Gary, Hyatt St, Sparkle Lake, Yorktown Heights, NX. Filed Jan. 10, 1963, Ser. No. 256,709 8 Claims. (Cl. 20-49) This invention relates to a braking mechanism, and more particularly to such mechanism as used in hangar or other large doors.

Hangar doors are customarily mounted on tracks, and the driving and braking forces for moving or stopping the door are applied through the wheels on which it rides. This method of braking produces considerable wear and tear on both wheels and rails, often resulting in flat wheels, and is not capable of stopping the door in an accurately predictable manner.

A general object of the invention is to provide an improved braking mechanism for such doors.

Another object is to provide a braking mechanism in which the maximum travel of the door is accurately gauged and its stopped position is closely determined.

In the braking mechanism of the invention, the kinetic energy of the door is converted into potential energy by causing the door to lift itself at the braking point, whereupon the door is then allowed to settle back to its original level. The ratio between vertical and horizontal travel during this action is accurately determined, setting an inherent maximum for the door movement for the frictionless case. Friction surfaces for dissipating the energy during these movements of the door are provided and involve no wear and tear on wheel or rail.

A braking mechanism embodying the invention in a preferred form will now first be described with reference to the accompanying drawing, and the features forming the invention will then be pointed out in the appended claims.

In the drawing:

FIG. 1 is a schematic elevation showing the lower part of a door equipped with the braking mechanism of the invention;

FIGS. 2 and 3 are views similar to FIG. 1, but show the manner of applying the brakes in the two directions of movement of the door;

FIG. 4 is a sectional view on the line 44 of FIG. 6 and on a larger scale, showing a form of braking mechanism in side elevation;

FIG. 5 is an end elevation of the mechanism of FIG. 4;

FIG. 6 is a cross section on the line 6-6 of FIG. 4; and

FIG. 7 is a detail fragmentary plan view looking in the direction of the arrows 77 of FIG. 4.

Referring to FIGS. 1-3 of the drawing, the door 1 may be a hangar door of any required dimensions, as, for example, thirty feet or so in width and fifteen feet or more in height and correspondingly heavy, as, for example, about forty tons in weight, being guided at the top (not shown) in the usual way and supported on a rail 2 by means of flanged wheels 3 and 4. As will be understood, the door is driven by electric motor drive means of usual type and at speeds of around one foot per second. With the dimensions and speed just mentioned as illustrative, the kinetic energy of the moving door may be around twelve hundred foot pounds.

In braking the door, wedges 5 and 6 are utilized, these wedges having cooperating surfaces slanted at a convenient angle, which may be about 10 (this value being assumed in the following description by way of example) to the horizontal. The wedge angle may vary in a range from about 515, depending upon such factors as weight of door, velocity, ability of the elements to with- 3,2l7,36? Patented Nov. 15, 1965 stand shock and specific requirements as to the distance of travel. The Wedge 5 is double and may cooperate also with a second wedge 7 for braking the door when moving in the opposite direction.

The braking of the door involves the pushing of the wedge 6 (or 7) between the wedge 5 (which is rigidly connected to the door) and the rail 2, so that as the door continues to travel it rides upon the wedge 6 (FIG. 2) or on the wedge 7 (FIG. 3) if the door is travelling in the opposite direction.

Once the wedge 6 has been pushed into place, further travel of the door lifts the wheel 3 free of the track 2 and lifts the door about .176 inch per of travel parallel to the rail (for a 10 wedge) and lifts the center of gravity (which is positioned over a point midway of the wheels) by about half this amount, to a point where its kinetic energy is entirely converted into potential and frictional energy. The frictional loss between the cooperating wedge surfaces is sufficient to dissipate a major part of the kinetic energy, so that the theoretical door travel of 2.1 (for the frictionless case) necessary to dissipate the door kinetic energy would not be attained. The door, once stopped by the wedge, will settle back, part of the potential energy being consumed in overcoming friction, the balance being converted into kinetic energy but of such small magnitude as to require practically no travel of the door in the reverse direction beyond the point where the wheels engage the rails and the wedges cease to support the door.

Further details of the operation of the braking mechanism of the invention will be given in connection with the following detailed description of the braking mechamsm.

The braking mechanism is largely enclosed within a space between channels 10 (FIGS. 4-6), secured to the upper door structure 11 as by bolts 12. A block 13 secured to the channels 10 and superstructure 11 as by means of some of the bolts 12 has welded to its a pair of depending side plates 14, between which is secured the upper stationary wedge block 5 as by means of screws 15. Wedge block 5 has a slant surface 5-F used in braking the movement in one direction and a similar surface 5R used for braking in the other direction, each of these surfaces being slanted at an angle of about 10 to the horizontal. The wedge block 6 is recessed along its lower edge so as to fit over the rail 2 as shown in FIG. 6. This maintains alignment of the wheel 3 with the rail when the brake is in operation and the wheel is lifted free.

The rail engaging surface 16 of the wedge is horizontal and its upper surface 17 is slanted at the same angle as the surface 5F of the wedge 5. An Oilite or other friction pad 18 is secured to the upper surface of the wedge 6, being held thereon and fixed thereto by blocks 19. The wedge 6 has laterally projecting ears 2t) engaging against the side plate 14 as shown in FIG. 7 to limit the wedge movement in the extreme position of the parts. A short link 25 pivotally connected to the wedge at 26 is, in turn, pivotally connected at 27 to an arm 28, which is, in turn, pivotally carried on shaft 29 journaled in the side plates 14-. A bar 30 i pivotally connected to arm 28 at 31 and to a similar arm 28 associated with the wedge 7. Springs 32, 32' attached at one end to clips 33, 33 and at the other to a post 34 tend to center the wedge arrangement in the disengaged position of FIG. 1. A pair of solenoids 35, 35 pivotally connected to the top of the post 34 at 36 have their plungers 37, 37' pivotally connected at 38, 38 to the extreme upper ends of the arms 28, 28'. The elements associated with the wedges 6 and 7 being similar and identified by similar reference numerals, the operation of the parts associated with the wedge '7 will be apparent from a description of those associated with the 3 wedge 6. It will be noted that wedge 6 is shown in FIG. 4 in the extreme position of engaging movement, wedge 7 being symmetrically mounted will be in the extreme position of disengaging movement.

The wedges 6 and 7 are guided in their movements by means of grooves 40, 40 formed in the side plates 14 and receiving ribs 41, 41' formed on the side faces of the wedges, so that the wedge moves in parallelism to the upper wedge surface 5F (or 5-R, as the case may be).

When the door is to be stopped, assuming it is moving in the forward direction (to the right in FIG. 1), solenoid 35 is energized, forcing the wedge 6 back (to the left) under upper wedge surface 5-F and against the rail 2. At this time, the arm 28 will be at a position about half way between that shown in FIG. 4 and the vertical or neutral position for the parts. Wedge 5 will now slide up the Oilite pad 18 of wedge 6 until a point is reached where the door stops (somewhat short of the limit position of FIGS. 4 and 7), the arm 28 and connected parts moving idly so as to permit this movement. The wedge materials are selected so that the coefficient of friction between surface 5-F and the friction pad 18 is materially less than the coefficient of friction between the wedge 6 and rail 2, thus insuring that the wedge 6 when once pushed into place remains stationary on the rail while the door rides up on the upper slanted surface of the wedge. The coeflicient of friction between the Oilite pad 18 and the surface 5-F may be approximately .10 as compared with a coefficient of friction between the lower surface of the wedge and the rail 2 of about 0.4 or more.

The wheels 3, 4 being located symmetrically with respect to the center of gravity of the door and the brake mechanism being positioned close to the wheel 3, the lifting of the center of gravity of the door will be approximately one-half of the amount of lifting at the brake as member 5 rides up the wedge 6. For simplicity, the action may be discussed on the assumption that half the weight of the door is supported by the wedge, any relocation of parts, which introduces a different weight distribution, merely introducing a proportionality factor which does not materially affect the following analysis.

As will be apparent, the riding up on the wedge 6 of the member 5 and door supported thereby involves the dissipation of part of the kinetic energy of the door due to the friction between parts, the amount of energy thus consumed equalling half the weight of the door multiplied by the horizontal distance travelled and by the coefficient of friction, while the remainder of the kinetic energy is converted into potential energy equal to half the weight of the door multiplied by the horizontal distance travelled and by the tangent of the wedge angle. Since the kinetic energy of the door with given velocity is the weight of the door multiplied by the square of its velocity and di vided by twice the gravitational constant (32.2 ft./sec. it is apparent that for given coefficient of friction and given velocity of the door, all factors are determined. Assuming a door velocity of one foot per second, which is a normal value, and a coefiicient of friction between members 5 and 6 of 0.10, which is a practical low value for the materials specified, the horizontal travel from the point where one wedge surface engages the other until all of the door kinetic energy is dissipated is 0.112 feet or 1.34 inches. With a coefficient of friction of 1.5 (which is a maximum value for the materials specified), this horizontal travel is somewhat reduced and amounts to 1.14 inches. It is apparent that the braking system is capacitated to stop the door in a reliable manner in about one and one-quarter inches horizontal travel from the point of application of the brake.

The coefficient of friction between the Wedge surfaces being less than the tangent of the wedge angle (e.g., tan 10 =.1765), the door will now slide back down the wedge until the wheel 3, again, comes in contact with the rail and takes over the support of the door. During this return process, there is a further dissipation of energy due to friction, substantially equal to the amount consumed in riding up the Wedge, so that the door returns to the rail with a very much reduced kinetic energy and is stopped substantially dead by the drive motor brake mechanism without subjecting the wheel to any abuse. With a coefiicient of friction of .10 between the wedge surfaces, the kinetic energy of the door at the instant the wheel comes back into contact with the rail is reduced to about thirty-six percent of its original value, while with a coefiicient of friction of .15, this reduction is to about eight percent. Where a wedge angle differing from the assumed angle of 10 is employed, friction materials having different coefficients of friction may be substituted, so as to insure the proper movement of the door up the Wedge and return to the rail, and also that the wedge remain stationary with respect to the rail during this process.

What is claimed is:

1. In a sliding door construction having a door, a rail, and wheels rotatably mounted on the door and supporting the same on the rail, a braking mechanism comprising a member fixed to the door and having a lower friction surface slanted at a predetermined angle with respect to the rail, a movable wedge member having a wedge angle the same as the said predetermined angle, the said movable wedge member having an upper surface for slidably engaging the said friction surface and a flanged bottom for fitting over the rail, means movably supporting the wedge member on the door for movement between an inactive position where it is spaced from the rail and a braking position where it engages both the rail and the said friction surface, and comprising vertical side plates fixed to the door at each side of the friction surface, and said plates and movable wedge element having cooperating rib and groove elements extending parallel to said friction surface for guiding the movable wedge member from said inactive position to said braking position and beyond the said braking position, thereby permitting movement of the door and inclined surface upwardly on the wedge, and operating means for moving the wedge member from inactive to active position, the said means having an operating stroke bringing the wedge into contact with the lower surface of said member and with the rail and also hav ing overtravel permitting further movement of the door with respect to the wedge to the said point where it stops, the coefficient of friction between the wedge and slant surface being less than the tangent of the wedge angle, whereby the door rides up the wedge in braking position to a point where it stops, lifting a said wheel off the rail, and then slides back down to bring the wheel back on to the rail, the coefficient of friction between the wedge and rail being greater than the first mentioned coefficient of friction, whereby the wedge in braking position remains stationary with respect to the rail, and the dissipation of initial kinetic energy in friction between the upper surface of the said wedge member and the said friction surface reduces the kinetic energy of the door upon return of the wheel to the rail to a value such that it may be stopped substantially dead.

2. Braking mechanism according to claim 1, in which the Wedge has a replaceable friction pad engaging the said slant surface.

3. Braking mechanism according to claim 1, comprising also means for returning the said movable wedge member to its said inactive position.

4. Braking mechanism according to claim 3, comprising spring means for returning the movable wedge member to inactive position.

5. Braking mechanism according to claim 1, comprising also stop means for limiting movement of said movable wedge member beyond the said braking position.

6. In a sliding door construction having a door, a rail, and wheels rotatably mounted on the door and supporting the same on the rail, a braking mechanism comprising a member fixed to the door and having lower fric tion surfaces slanting downwardly toward each other at a predetermined angle with respect to the rail, a pair of oppositely facing movable Wedge members having wedge angles the same as the said predetermined angle, each said movable wedge member having an upper surface for slidably engaging a said friction surface and a flanged bottom for fitting over the rail, means movably supporting the said Wedge members on the door for movement between inactive positions where they are spaced from the rail and braking positions where they engage the rail and the said friction surfaces, and comprising vertical side plates fixed to the door at each side of the friction surfaces, the said plates and movable wedge elements having cooperating rib and groove elements extending parallel to said friction surfaces for guiding the movable wedge members from said inactive positions to said braking positions and beyond the said braking positions, and operating mechanism comprising a linkage connected to the said wedges, means normally holding the linkage in a central neutral position where both wedges are inactive, operating means for selectively moving the linkeage to engage each of the said two wedges, for braking movement in the forward and reverse directions, respectively, the said operating mechanism having overtravel, whereby the door may ride up and back down a said Wedge, the coefiicient of friction between said wedges and friction surfaces being less than the tangent of the said predetermined angle, and the coefficient of friction between the said wedges and the rail being greater, whereby the wedge in braking position remains stationary on the rail and the dissipation of initial kinetic energy in friction between the upper surfaces of the said wedge members and the said friction surfaces reduces the kinetic energy of the door upon return of the wheel to the rail to a value such that it may be stopped substantially dead.

7. Braking mechanism according to claim 6, comprising also spring means yieldably urging the said linkage toward the said central neutral position, whereby on return of the said wheel to the rail the wedges are returned to normal inactive position.

8. Braking mechanism according to claim 6, comprising also stop means on said wedges for engaging the said member and limiting movement of the Wedges in the braking direction.

References Cited by the Examiner UNITED STATES PATENTS 553,973 2/1896 Whitney 188-41 660,645 10/1900 Lowe et al. 188-41 2,423,129 I 7/1947 Tobias 20--19 X 2,599,747 6/1952 Craigon 2019 FOREIGN PATENTS 649,422 8/ 1837 Germany. 66 2/ 1874 Italy.

HARRISON R. MOSELEY, Primary Examiner. 

1. IN A SLIDING DOOR CONSTRUCTION HAVING A DOOR, A RAIL, AND WHEELS ROTATABLY MOUNTED ON THE DOOR AND SUPPORTING THE SAME ON THE RAIL, A BRAKING MECHANISM COMPRISING A MEMBER FIXED TO THE DOOR AND HAVING A LOWER FRICTION SURFACE SLANTED AT A PREDETERMINED ANGLE WITH RESPECT TO THE RAIL, A MOVABLE WEDGE MEMBER HAVING A WEDGE ANGLE THE SAME AS THE SAID PREDETERMINED ANGLE, THE SAID MOVABLE WEDGE MEMBER HAVING AN UPPER SURFACE FOR SLIDABLY ENGAGING THE SAID FRICTION SURFACE AND A FLANGED BOTTOM FOR FITTING OVER THE RAIL, MEANS MOVABLY SUPPORTING THE WEDGE MEMBER ON THE DOOR FOR MOVEMENT BETWEEN AN INACTIVE POSITION WHERE IT IS SPACED FROM THE RAIL AND A BRAKING POSITION WHERE IT ENGAGES BOTH THE RAIL AND THE SAID FRICTION SURFACE, AND COMPRISING VERTICAL SIDE PLATES FIXED TO THE DOOR AT EACH SIDE OF THE FRICTION SURFACE, AND SAID PLATES AND MOVABLE WEDGE ELEMENT HAVING COOPERATING RIB AND GROOVE ELEMENTS EXTENDING PARALLEL TO SAID FRICTION SURFACE FOR GUIDING THE MOVABLE WEDGE MEMBER FROM SAID INACTIVE POSITION TO SAID BRAKING POSITION AND BEYOND THE SAID BRAKING POSITION, THEREBY PERMITTING MOVEMENT OF THE DOOR AND INCLINED SURFACE UPWARDLY ON THE WEDGE, AND OPERATING MEANS FOR MOVING THE WEDGE MEMBER FROM INACTIVE TO ACTIVE POSITION, THE SAID MEANS HAVING AN OPERATING STROKE BRINGING THE WEDGE INTO CONTACT WITH THE LOWER SURFACE OF SAID MEMBER AND WITH THE RAIL AND ALSO HAVING OVERTRAVEL PERMITTING FURTHER MOVEMENT OF THE DOOR WITH RESPECT TO THE WEDGE TO THE SAID POINT WHERE IT STOPS, THE COEFFICIENT OF FRICTION BETWEEN THE WEDGE AND SLANT SURFACE BEING LESS THAN THE TANGENT OF THE WEDGE ANGLE, WHEREBY THE DOOR RIDES UP THE WEDGE IN BRAKING POSITION TO A POINT WHERE IT STOPS, LIFTING A SAID WHEEL OFF THE RAIL, AND THEN SLIDES BACK DOWN TO BRING THE WHEEL BACK ON TO THE RAIL, THE COEFFICIENT OF FRICTION BETWEEN THE WEDGE AND RAIL BEING GREATER THAN THE FIRST MENTIONED COEFFICIENT OF FRICTION, WHEREBY THE WEDGE IN BRAKING POSITION REMAINS STATIONARY WITH RESPECT TO THE RAIL, AND THE DISSIPATION OF INITIAL KINETIC ENERGY IN FRICTION BETWEEN THE UPPER SURFACE OF THE SAID WEDGE MEMBER AND THE SAID FRICTION SURFACE REDUCES THE KINETIC ENERGY OF THE DOOR UPON RETURN OF THE WHEEL TO THE RAIL TO A VALUE SUCH THAT IT MAY BE STOPPED SUBSTANTIALLY DEAD. 